The spatiotemporal organisation as a means of control of regulatory T cell functions in autoimmunity

Abstract

CD4+ effector (Teff) and regulatory (Treg) T cells play different roles in the immune system. Teffs promote innate and adaptive immune responses, while Tregs suppress immune responses, maintain immunological tolerance and prevent autoimmune diseases. Naïve CD4+ T cell can be induced in vitro to become Teffs or inducible Tregs (iTregs). This work focused on comparing the spatiotemporal organisation of T cell signalling intermediates upon activation of Teffs and iTregs, using the Tg4 murine model of experimental autoimmune encephalomyelitis. Live cell imaging data of Tg4 Teffs were previously acquired. Compared to Teffs, iTregs were found to show impaired spatiotemporal patterning of LAT, TCR-ζ and F-actin, suggesting their activation to be defective. T cell-APC couples formed by iTregs were found to be less stable. iTregs show a reduced ability to secrete IFN-γ and tend to secrete more IL-10 than Teffs. To investigate whether iTreg function can be controlled by proximal T cell signalling, CTLA-4 and PD-1 coinhibitory pathways, the spatiotemporal distribution of LAT during iTreg activation were manipulated.

Results show that blocking CTLA-4 and PD-1 significantly inhibited iTreg generation. Dual blockade of CTLA-4 and PD-1 was found to improve cell coupling and partially enhance LAT accumulation at the T cell-APC interface. Previous work has shown that fusing LAT with the PKC-θ V3 or Vav1 SH3SH2SH3 domain enhances LAT central accumulation at the interface under attenuated T cell stimulation. Here we show that in iTreg activation, fusion with PKC-θ V3 excessively enhanced LAT overall accumulation at the interface, but slightly reduced their IFN-γ and IL-10 secretion, while fusion with Vav1 SH3SH2SH3 fully restored LAT overall accumulation at the interface, and slightly enhanced IL-10 secretion. Both conditions improved cell coupling. These data indicate that blocking coinhibitory pathways and enhancing LAT spatiotemporal organisation improve iTreg activation, but regulate their immunosuppressive function to a small extent.

Date of Award	26 Nov 2020
Original language	English
Awarding Institution	The University of Bristol
Supervisor	Christoph Wuelfing (Supervisor)